Building an REU for C64
Charles Richmond
expansion unit (REU) for the Commodore 64 using a 256k
30-pin SIMM??? I think I can get some of these SIMM's
quite cheaply, and a couple would give half a meg in
an expansion unit...
--
+----------------------------------------------------------------+
| Charles and Francis Richmond richmond at plano dot net |
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White Flame (aka David Holz)
news:3F8F301D...@comcast.net...
> Are there any plans on the internet for building a RAM
> expansion unit (REU) for the Commodore 64 using a 256k
> 30-pin SIMM??? I think I can get some of these SIMM's
> quite cheaply, and a couple would give half a meg in
> an expansion unit...
The problem with building an REU is that Commodore put a custom DMA
controller chip in there; it's not just a stack of RAM sitting on the
expansion port like, for example, the GeoRAM.
--
White Flame (aka David Holz)
http://www.white-flame.com/
(spamblock in effect)
tendim
> The problem with building an REU is that Commodore put a custom DMA
> controller chip in there; it's not just a stack of RAM sitting on the
> expansion port like, for example, the GeoRAM.
Do PIC's or other cheap embedded processors not yet exist that could
mimic the functionality of the DMA? (Wasn't it called an REC? Or am I
mistaking it for something else?)
-cr/rpg
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tendim
remove all capitals from eMail address for replies
White Flame (aka David Holz)
news:1g2y610.m4kuyoylwr9cN%pat...@NOtendim.cjb.netSPAM...
> Do PIC's or other cheap embedded processors not yet exist that could
> mimic the functionality of the DMA? (Wasn't it called an REC? Or am I
> mistaking it for something else?)
Yeah, it's called an REC. If you get something that's fast enough to
twiddle 16 address lines and 8 data lines to the 64, simultaneously with 24
address lines and 8 data lines in the REU, all at 1MHz, you could probably
pull it off with a microcontroller.
--
White Flame (aka David Holz)
Pheuque
adapter. Looking for an REU or even planning on getting my RAMlink Repaired
at some point, it's power consumption and limited storage size seems like
such a waist.
Hooking up a CF card to a C64 would give it more than enough storage space
to be an instant on machines for any application you could think of.
I wonder if there's a way to replace the ROM's and actually boot from a CF
Card.
"White Flame (aka David Holz)" <whitef...@y.a.h.o.o.com> wrote in message
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Peter van Merkerk
> > controller chip in there; it's not just a stack of RAM sitting on
the
> > expansion port like, for example, the GeoRAM.
>
> Do PIC's or other cheap embedded processors not yet exist that could
> mimic the functionality of the DMA? (Wasn't it called an REC? Or am
I
> mistaking it for something else?)
Maybe, though a FPGA or EPLD chip would be IMO a more obvious choice.
--
Peter van Merkerk
peter.van.merkerk(at)dse.nl
Maciej Witkowiak
> Hooking up a CF card to a C64 would give it more than enough storage space
> to be an instant on machines for any application you could think of.
You can hook up CF through IDE adapter to IDE64 (or any other IDE interface
for C64/128). Anyway, access time difference between CF and IDE disk is not
something you would notice. At least not in up-to-64KB transmissions.
> I wonder if there's a way to replace the ROM's and actually boot from a CF
> Card.
You would have to replace the ROMs to code that actually boots from a CF :).
But there is problem - such system would load itself to RAM while all software
expects that ROM contents can't be changed.
ytm
--
Najlepsza sygnatura to brak sygnatury.
Wolfgang Moser
Peter van Merkerk wrote:
>>>The problem with building an REU is that Commodore put a custom DMA
>>>controller chip in there; it's not just a stack of RAM sitting on
>
>>Do PIC's or other cheap embedded processors not yet exist that could
>>mimic the functionality of the DMA? (Wasn't it called an REC? Or am
>
> Maybe, though a FPGA or EPLD chip would be IMO a more obvious choice.
some part of this work was already done by Rainer Buchty.
There were already some discussions in the past, if and
how the REC (RAM expansion controller) of the Commodore
17xx REUs could be rebuild, so that:
a) the greatest compatibility can be reached
b) further expansions are possible through an 8-bit
bank register (instead of only 3 Bit)
It was said here, and I think, the earlier discussions
also came to this conclusion, that a microcontroller
based solution would be not the right concept for
doing so.
In my opinion, a CPLD (complex programmable logic
device) with somewhat between 64 and 128 macrocells
should be enough to reach the goal.
Some work has already been done by Rainer Buchty as I said
above. He wrote up some logic equations in VHDL, that mimic
the basic REC functionality. Check out the source file at
Funet.FI:
http://www.funet.fi/pub/cbm/documents/projects/memory/c64/rec.vhdl
Rainer actually did not implement his euqations into a
concrete hardware and so, his theoretical writeup isn't
tested until now.
Another job to do, would be to write a compatibility test
suite. Somewhere in the late 1980'ties I recognized a bug
with the 1764 REU, that I named "half autoload bug".
This bug for example is emulated by the VICE emu, but as
Rainer said to me, his equations don't contain "support"
for this issue.
So, you all can see, some work is already done, but there
are still some jobs to do; the whole thing wouldn't be
impossible as Rainer proofed with his concept, but
nevertheless it's a lot of work.
Womo
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Göran Sandström
(FPGA you know).
It's actually ment to be a "musicbox" as there sit two 16 stereo DACs in it.
If someone knows a good place to put up some pictures, I've got plenty of
them if someone is interested in a look.
Did I mention it has 32 MB of RAM? ;-)
/Göran
"Peter van Merkerk" <mer...@deadspam.com> skrev i meddelandet
news:bmohco$orsjt$1...@ID-133164.news.uni-berlin.de...
RajW
reading an article about it in Transactor magazine. So I looked it up
and scanned it for you guys to assist with your research and
questions.
This is from the December 1988: Vol 9, Issue 2 Transactor.
Title: Care and Feeding of the C256 (Strange title!)
This link is on one of my high-bandwidth servers.
File size is... 5593.08KB (5.6MB)
http://www.woodland-brooke.org/cbm/transactor-c64-ramexp.zip
It is a high resolution scan reduced to 200dpi in PNG format.
/*Raj*/
Six of DLoC
@comcast.net:
Soci/Singular did a hack like that. Unfortunately, I can't find his
schematics anywhere. I'm slowly trying to come up with a hack along those
lines. I figured on pulling the RAM from the C64, and taking the address
and data lines directly, eliminating the hardware that converts the signals
for SRAM. I'm not very well versed in circuit design, though, so it's
still all theory.
Peter van Merkerk
> > expansion unit (REU) for the Commodore 64 using a 256k
> > 30-pin SIMM??? I think I can get some of these SIMM's
> > quite cheaply, and a couple would give half a meg in
> > an expansion unit...
>
> schematics anywhere. I'm slowly trying to come up with a hack along those
> lines. I figured on pulling the RAM from the C64, and taking the address
> and data lines directly, eliminating the hardware that converts the
signals
> for SRAM. I'm not very well versed in circuit design, though, so it's
> still all theory.
What are you trying to achieve? A RAM expansion or RAM with battery backup?
Six of DLoC
news:bn3sfr$ss388$1...@ID-133164.news.uni-berlin.de:
Just a simple RAM expansion. Unfortunately, I don't really understand how
DRAM works, but I'm well versed in dealing with SRAM.
S.o.D.
Pheuque
I think the need for refresh on the DRAM would make it impossible. After
all, wasn't that the purpose of the RAMlink by CMD? to make DRAM simm
axpansion available for Commodore? As a beta tester I remeber just how much
work went into creating it and getting working.
I wonder if it's possible these days to emulate the Commodore REC with a
FPGA. It would be real nice to get a new 1750 compatible REU.
"Six of DLoC" <sixSP...@darklordsofchaos.com> wrote in message
news:Xns941E7E5BABC...@63.223.8.240...
> Just a simple RAM expansion. Unfortunately, I don't really understand how
> DRAM works, but I'm well versed in dealing with SRAM.
>
> S.o.D.
>
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Wolfgang Moser
> I wonder if it's possible these days to emulate the Commodore REC with a
> FPGA. It would be real nice to get a new 1750 compatible REU.
Please refer to:
http://groups.google.de/groups?selm=bmp2t0%2460d%241%40online.de
and perhaps also to:
http://groups.google.de/groups?selm=3b49c023.1811009%40news.cc.ukans.edu
that may be answer some of your questions.
mike
something else?
In article <bmntk7$2nq2$1...@barad-dur.nas.com>, "White Flame \(aka David Holz\)"
<whitef...@y.a.h.o.o.com> writes:
>
>"tendim" <pat...@NOtendim.cjb.netSPAM> wrote in message
>news:1g2y610.m4kuyoylwr9cN%pat...@NOtendim.cjb.netSPAM...
>> Do PIC's or other cheap embedded processors not yet exist that could
>> mimic the functionality of the DMA? (Wasn't it called an REC? Or am I
>> mistaking it for something else?)
>
>Yeah, it's called an REC. If you get something that's fast enough to
>twiddle 16 address lines and 8 data lines to the 64, simultaneously with 24
>address lines and 8 data lines in the REU, all at 1MHz, you could probably
>pull it off with a microcontroller.
>
Mike
University Place Commodore User Group (UPCHUG)
Tacoma, WA USA
Robert Bernardo
> IFIRC SSI put out their own REU, did they use Commodore's REC or did they use
> something else?
They took a smaller Commodore REU, expanded it to 512K, and
slapped a silver sticker on the case which called it the 1750 Clone. And
so, they were using the Commodore REC.
Truly,
Robert Bernardo
Fresno Commodore User Group
http://videocam.net.au/fcug
Wolfgang Moser
Robert Bernardo wrote:
> On Sun, 26 Oct 2003, Mike wrote:
>
>>IFIRC SSI put out their own REU, did they use Commodore's REC or did they use
>>something else?
Yes, they put the original Commodore 8726 REC into their clone.
> They took a smaller Commodore REU, expanded it to 512K, and
> slapped a silver sticker on the case which called it the 1750 Clone. And
> so, they were using the Commodore REC.
I don't have some exhibits for this, but I heard, that they in
fact bought out remaining stocks of the 8726 REC from Commodore.
No need for disrupting working 1700/64 devices.